For the past decades, amputees have worn tubular sock-like articles over their residual limbs to provide additional comfort to the amputee when wearing a prosthetic limb. For many years, the tubular sock-like articles were formed of natural materials, such as cotton, wool, and cotton-wool blends; however, as synthetic materials become increasingly popular as a material of choice to form articles of apparel, including socks, the tubular sock-like articles were increasingly fabricated using synthetic materials.
As is known, an amputee is typically fitted with a prosthetic member to be worn on the residual limb. In a below-knee (BK) prosthesis, an amputee's stump tends to pivot within a socket of the prosthesis. During ambulation, the stump will come up in the socket of the prosthesis until the means for attaching the prosthetic to the wearer causes the prosthetic to lift with the stump. The wearer then completes a walking motion or other movement by repeatedly lifting the prosthetic up and then placing it back down in a different location to effectuate movement of the wearer's body.
Most of the available cushioned residuum socks (prosthetic liners) that are currently available have a tubular or conical construction and do not provide a form fit of the amputee's residuum since the residuum stump typically does not contain a completely uniform shape. For example, while the residuum stump generally has a roughly conical shape, the residuum stump will often have recessed areas in certain locations. On a below knee, left side residual limb, the recessed area is often more pronounced on the right side of the tibia bone, while for right side residual limbs, the more pronounced recessed area is on the left side of the bone. In both instances, the side opposite the side with the more pronounced recessed area will also contain a recessed area to a lesser degree and further the greatest recess typically occurs immediately below the patella, one either side. Conventional prosthetic liners do not accommodate the non-uniform nature of the residuum and this can result in the amputee experiencing wearing discomfort due to the non-uniform fit.
When the amputee uses a prosthetic device, the amputee simply attaches a prosthetic limb to their residual limb by means of a rigid socket, liner, and a suspension means. The rigid socket can be custom fabricated to match the shape of the intended user's residual limb and can be formed from a variety of different materials, including but not limited to thermoplastic materials, fiber-reinforced thermoset materials, as well as wood and metals. Because the residual limb interfaces with the hard, rigid prosthetic limb, this interface can become an area of discomfort over time since this interface is a load bearing interface between the residual limb and the prosthetic limb. In order to alleviate this discomfort and provide a degree of cushioning to lessen the impact of the load, prosthetic liners (socks) are used as interface members between the hard prosthetic socket and the residual limb in order to increase comfort.
Traditionally, several methods have been used to apply a cushion material to an article, such as a sleeve member intended for use as a prosthetic liner for placement over a residual limb. One process uses conventional dipping techniques in which the closed distal end of the sleeve member is dipped into cushioning material which exists in a liquid or molten state. The sleeve member is dipped into the cushioning material at a prescribed angle relative to the surface of the molten or liquified cushioning material so that the cushioning material extends up the sleeve member from the closed distal end to a further extent on the side of the sleeve member. The sleeve member is then manipulated in the liquified or molten cushioning material to effectively coat the surface of the sleeve member with the cushioning material. When the cushioning material is applied in this manner, the sleeve member has likely been inverted so that the interior surface is actually the exterior surface that is exposed to the liquified or molten cushioning material. After application of the cushioning material by dipping the inverted sleeve member into the liquified or molten cushioning material and permitting the cushioning material to sufficiently cool, the coated sleeve member is then inverted again so that the surface that has the cushioning material applied thereon becomes the interior surface of the cushioned sleeve member.
Prior to inserting (i.e., dipping) the sleeve member into the liquified or molten cushioning material, a mandrel or the like is inserted into the inverted sleeve member to stretch and shape the sleeve member to its intended tubular shape. The mandrel is thus a tool that permits a person to dip the sleeve member into the liquified or molten cushioning material without exposing the person to any unnecessary risks. The mandrel is then manipulated so that the exposed surfaces of the sleeve member are in contact with the cushioning material. In order to increase the thickness, the sleeve member is repeatedly dipped so as to effectively build-up the thickness of the cushioning material.
One of the disadvantages of the dipping process is that control of the thickness of the cushioning material is rather an arduous task and is fairly imprecise due to the thickness being built-up to a desired thickness by repeatedly dipping the sleeve member into the coating. Further, the sleeve member must be inverted before and after the cushioning material is applied to the sleeve member. After the cushioning material has been applied and allowed to cool, the final inversion of the cushioned sleeve member can cause crazing, folding or other imperfections to form in the layer of the cushioning material.
In addition to the application of the cushioning material to the sleeve member by dipping the sleeve member into liquified or molten cushioning material, the cushioning material can be “painted” onto the sleeve member or it is also possible to dissolve the polymeric material in a solvent followed by application of the solvent to the sleeve member with subsequent evaporation of the solvent, thereby leaving a layer of cushioning material formed on the sleeve member. This process is also marked by a degree of imprecision with respect to forming the cushioning material to a desired thickness.
Another process for applying a cushioning materials is an “open pour” process in which the cushioning material is poured into a mold and settles therein due to gravitational forces. This process does not involve compression of the material and is marked by the following disadvantages: it is difficult to precisely control the thickness and a poor bond typically results between the fabric and the material.
Further, all of the above-methods do not permit the thickness of the cushion layer to be specially contoured in select regions of the article for purpose of providing more or less comfort and protection in these regions.
Thus, there is still a need in the art for a simple yet effective process for applying a layer of cushioning material to a surface of an article, whereby the thickness of the cushion layer can be controlled to a high degree of precision and the profile of the cushion layer can also be controlled and varied depending upon the application.